88 EDWARD STEIDTMANN 



the country rock which the granites invaded must have been nearer 

 the condition of crystallization or fusion than the granites, and that 

 the Laurentian granites are batholiths rather than re-fused sedi- 

 ments or portions of the original crust of the earth. 



Lindgren' states that the principal pre-Cambrian ores of North 

 America are iron, copper, nickel, gold, and silver. The iron ore 

 types are : magnetite and ilmenite of igneous origin, and hematites 

 of sedimentary and igneous origin, which have been concentrated 

 by surface waters. The copper, nickel, and silver of the Lake 

 Superior region and the copper ores of the South are connected with 

 basic igneous rock. The gold quartz veins of the south are related 

 to granitic intrusions. 



Newland^ states that the iron ores mined in Sweden are all pre- 

 Cambrian magnetites associated with crystalline schists and acid 

 igneous rocks. There are also some low-grade, gabbroic, titanifer- 

 ous magnetite silicate rocks, and bog lake deposits, the latter 

 famous as exemplifications of present-day ore deposition, but these 

 are not mined. 



Most of the ore comes from central Sweden. A considerable 

 portion of this is unique for its low phosphorus content, and 

 because of its exceptional qualities can be mined from very small 

 deposits on a miniature scale. The ore is reduced in charcoal 

 furnaces. Nearly half of the output of central Sweden is high 

 phosphorus ore from Grangesberg. The high phosphorus ores are 

 all exported, since there are no coals in Sweden suitable for furnaces. 

 The ores of central Sweden occur in association with sediments, 

 leptites, and gneisses which form winding lenses between massive 

 intrusives. The ores at Norberg and Striberg consist of banded 

 magnetite quartz rocks with a sedimentary aspect. 



The Kiruna and Gellivare magnetite apatite deposits of Lapland 

 resemble the titaniferous ores of New York in their association with 

 sodic rocks. The ores at Gellivare are lenses, bands, and chimneys 

 in syenite, the entire mass showing regional metamorphism. The 



' W. Lindgren, " Metallogenetic Epochs," Jour. Can. Min. Inst., XII (1910), 

 102-13. 



^ D. H. Newland, "Notes on the Geology of the Swedish Magnetites," New York 

 State Museum Bull. 149, 1910, pp. 107-19. 



